Camptothecin is a topoisomerase I inhibitor originally isolated from the bark and stem of Camptothecaacuminata (Camptotheca, Happy tree), a tree native to China.
Camptothecin analogs having anti-cancer and anti-tumor properties are described in U.S. Pat. No. 6,136,978, hereby incorporated by reference in its entirety. In one aspect, these camptothecin analogs have the following general structure (Formula I) described in U.S. Pat. No. 6,136,978 (“'978 patent”):

where R1-R11 are defined as in the '978 (e.g., col. 3, line 35—col. 4, line 65).
Of particular interest is a camptothecin analog known as AR-67 or DB-67 ((20S)-10-hydroxy-7-trimethylsilylcamptothecin)) (Formula II) having the structure shown below:

Topoisomerases regulate the winding and unwinding of DNA strands. Camptothecins are DNA topoisomerase I inhibitors which stabilize single-strand breaks in DNA leading to apoptosis and cell death. A general scheme for synthesizing the compound of Formula I is provided in FIG. 1 of the '978 patent.
A known general scheme for synthesizing AR-67 (the compound of Formula II is shown below:

In this synthesis method, the starting material, 10-hydroxycamptothecin, is a natural product obtained from Camptothecaacuminate that requires special handling due to toxicity. In addition, the cost of this starting material is high. Thus, use of known synthesis methods for making the Camptothecin analogs of Formula I and, in particular, AR-67, may be cost prohibitive due the cost of the starting materials and special facilities and handling needed for the starting materials and intermediaries.
What is needed is an improved, less costly method for making, forming, or synthesizing the compounds of Formula I, including AR-67, with higher yields, fewer impurities, lower cost, and less risk.